U.S. patent application number 13/457684 was filed with the patent office on 2012-11-22 for transponder, repeater, and terminal equipment.
This patent application is currently assigned to HITACHI, LTD.. Invention is credited to Kenta Noda.
Application Number | 20120294605 13/457684 |
Document ID | / |
Family ID | 46062074 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120294605 |
Kind Code |
A1 |
Noda; Kenta |
November 22, 2012 |
TRANSPONDER, REPEATER, AND TERMINAL EQUIPMENT
Abstract
A transponder for performing bidirectional conversion between a
client-side signal used for communication to a client device and a
transmission path-side signal used for communication to a
transmission path, the transponder comprising: a client-side
interface for inputting/outputting the client-side signal; a
transmission path-side interface for inputting/outputting the
transmission path-side signal; a connection determining unit for
determining which of the another client-side interface and the
client device is coupled to the client-side interface; and a
transmission signal generating unit for outputting, in a case where
a state signal indicating a state on a transmission path side is
input to the transmission path-side interface, a transmission
signal indicating that the state signal has been input, from the
client-side interface, wherein: the transmission signal generating
unit changes a form of the transmission signal to be output from
the client-side interface, based on a determination result obtained
by the connection determining unit.
Inventors: |
Noda; Kenta; (Yokohama,
JP) |
Assignee: |
HITACHI, LTD.
Tokyo
JP
|
Family ID: |
46062074 |
Appl. No.: |
13/457684 |
Filed: |
April 27, 2012 |
Current U.S.
Class: |
398/11 ;
398/173 |
Current CPC
Class: |
H04B 10/079 20130101;
H04L 41/06 20130101; H04Q 2213/1301 20130101; H04Q 3/0062 20130101;
H04L 43/0811 20130101; H04L 43/0805 20130101 |
Class at
Publication: |
398/11 ;
398/173 |
International
Class: |
H04B 10/16 20060101
H04B010/16; H04B 10/08 20060101 H04B010/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 16, 2011 |
JP |
2011-109207 |
Claims
1. A transponder for performing bidirectional conversion between a
client-side signal used for communication to a client device and a
transmission path-side signal used for communication to a
transmission path, the transponder comprising: a client-side
interface for inputting/outputting the client-side signal, which is
coupled to one of another client-side interface and the client
device; a transmission path-side interface for inputting/outputting
the transmission path-side signal; a connection determining unit
for determining which of the another client-side interface and the
client device is coupled to the client-side interface; and a
transmission signal generating unit for outputting, in a case where
a state signal indicating a state on a transmission path side is
input to the transmission path-side interface, a transmission
signal indicating that the state signal has been input, from the
client-side interface, wherein: the connection determining unit has
a recognition signal output unit for outputting, from the
client-side interface, a recognition signal for determining that
the another client-side interface is coupled to the client-side
interface; the connection determining unit determines that the
another client interface is coupled to the client-side interface in
a case where the recognition signal is input to the client-side
interface; and the transmission signal generating unit changes a
form of the transmission signal to be output from the client-side
interface, based on a determination result obtained by the
connection determining unit.
2. The transponder according to claim 1, wherein: in a case where
the connection determining unit determines that the another
client-side interface is coupled to the client-side interface, the
transmission signal generating unit outputs the transmission signal
from the client-side interface; and in a case where the connection
determining unit determines that the client device is coupled to
the client-side interface, the transmission signal generating unit
stops an output of a signal from the client-side interface.
3. The transponder according to claim 2, wherein the state signal
includes a failure signal indicating that a failure has occurred on
the transmission path side.
4. The transponder according to claim 1, wherein: the recognition
signal output unit determines that connection to the transmission
path is established in a case where some signal is input to the
transmission path-side interface; the recognition signal output
unit outputs a predetermined signal different from the recognition
signal from the client-side interface in a case where the
recognition signal output unit determines that the connection to
the transmission path is established; and the recognition signal
output unit outputs the recognition signal in a case where the
recognition signal output unit determines that the connection to
the transmission path is established and in a case where a
predetermined signal is input to the client-side interface.
5. The transponder according to claim 1, wherein: the connection
determining unit has a response signal generating unit for
outputting, in a case where the recognition signal is input to the
client-side interface, a response signal with respect to the
recognition signal from the client-side interface; and the
connection determining unit determines that the another client-side
interface is coupled to the client-side interface in a case where
the response signal with respect to the recognition signal is input
to the client-side interface.
6. A repeater for relaying two transmission paths used for
communication of two opposing client devices, the repeater
comprising a first transponder coupled to one of the two
transmission paths and a second transponder coupled to another one
of the two transmission paths, wherein: the first transponder and
the second transponder perform bidirectional conversion between a
client-side signal used for communication to the client device and
a transmission path-side signal used for communication to the
transmission path; each of the first transponder and the second
transponder has a client-side interface for inputting/outputting
the client-side signal and a transmission path-side interface for
inputting/outputting the transmission path-side signal; the
client-side interface is coupled to one of another client-side
interface and the client device; the client-side interface of the
first transponder and the client-side interface of the second
transponder are coupled to each other, the one of the two
transmission paths is coupled to the transmission path-side
interface of the first transponder, and the another one of the two
transmission paths is coupled to the transmission path-side
interface of the second transponder; each of the first transponder
and the second transponder further has: a connection determining
unit for determining which of the another client-side interface and
the client device is coupled to the client-side interface; and a
transmission signal generating unit for outputting, in a case where
a state signal indicating a state on a transmission path side is
input to the transmission path-side interface of one of the first
transponder and the second transponder, a transmission signal
indicating that the state signal has been input, from the
client-side interface of the one of the first transponder and the
second transponder; the transmission signal generating unit outputs
the transmission signal from the client-side interface in a case
where the connection determining unit determines that the another
client-side interface is coupled to the client-side interface; the
transmission signal generating unit stops an output of a signal
from the client-side interface in a case where the connection
determining unit determines that the client device is coupled to
the client-side interface; the connection determining unit of the
each of the first transponder and the second transponder determines
that the another client-side interface is coupled to the
client-side interface; the transmission signal generating unit of
the one of the first transponder and the second transponder in
which the state signal is input to the transmission path-side
interface outputs the transmission signal from the client-side
interface to the client-side interface of the another one of the
first transponder and the second transponder; and the another one
of the first transponder and the second transponder outputs the
state signal from the transmission path-side interface in a case
where the transmission signal is input to the client-side
interface.
7. The repeater according to claim 6, wherein the state signal
includes a failure signal indicating that a failure has occurred on
the transmission path side.
8. The repeater according to claim 6, wherein: the connection
determining unit has a recognition signal output unit for
outputting, from the client-side interface, a recognition signal
for determining that the another client-side interface is coupled
to the client-side interface; the connection determining unit
determines that the another client interface is coupled to the
client-side interface in a case where the recognition signal is
input to the client-side interface; the recognition signal output
unit determines that connection to the transmission path is
established in a case where some signal is input to the
transmission path-side interface; the recognition signal output
unit outputs a predetermined signal different from the recognition
signal from the client-side interface in a case where the
recognition signal output unit determines that the connection to
the transmission path is established; and the recognition signal
output unit outputs the recognition signal in a case where the
recognition signal output unit determines that the connection to
the transmission path is established and in a case where a
predetermined signal is input to the client-side interface.
9. The repeater according to claim 6, wherein: the connection
determining unit has a response signal generating unit for
outputting, in a case where the recognition signal is input to the
client-side interface, a response signal with respect to the
recognition signal from the client-side interface; and the
connection determining unit determines that the another client-side
interface is coupled to the client-side interface in a case where
the output response signal with respect to the recognition signal
is input to the client-side interface.
10. Terminal equipment to be coupled to a client device and a
transmission path, the terminal equipment comprising a transponder
for performing bidirectional conversion between a client-side
signal used for communication to the client device and a
transmission path-side signal used for communication to the
transmission path, wherein: the transponder has a client-side
interface for inputting/outputting the client-side signal and a
transmission path-side interface for inputting/outputting the
transmission path-side signal; the client-side interface is coupled
to one of another client-side interface and the client device; the
client device is coupled to the client-side interface, and the
transmission path is coupled to the transmission path interface;
the transponder further has: a connection determining unit for
determining which of the another client-side interface and the
client device is coupled to the client-side interface; and a
transmission signal generating unit for outputting, in a case where
a state signal indicating a state on a transmission path side is
input to the transmission path-side interface, a transmission
signal indicating that the state signal has been input, from the
client-side interface; the transmission signal generating unit
outputs the transmission signal from the client-side interface in a
case where the connection determining unit determines that the
another client-side interface is coupled to the client-side
interface; the transmission signal generating unit stops an output
of a signal from the client-side interface in case where the
connection determining unit determines that the client device is
coupled to the client-side interface; and the transmission signal
generating unit stops the output of the signal from the client-side
interface in a case where the connection determining unit
determines that the client device is not coupled to the client-side
interface and in a case where the state signal is input to the
transmission path-side interface.
11. The terminal equipment according to claim 10, wherein the state
signal includes a failure signal indicating that a failure has
occurred on the transmission path side.
12. The terminal equipment according to claim 10, wherein: the
connection determining unit has a recognition signal output unit
for outputting, from the client-side interface, a recognition
signal for determining that the another client-side interface is
coupled to the client-side interface; the connection determining
unit determines that the another client interface is coupled to the
client-side interface in a case where the recognition signal is
input to the client-side interface; the recognition signal output
unit determines that connection to the transmission path is
established in a case where some signal is input to the
transmission path-side interface; the recognition signal output
unit outputs a predetermined signal different from the recognition
signal from the client-side interface in a case where the
recognition signal output unit determines that the connection to
the transmission path is established; and the recognition signal
output unit outputs the recognition signal in a case where the
recognition signal output unit determines that the connection to
the transmission path is established and in a case where a
predetermined signal is input to the client-side interface.
Description
CLAIM OF PRIORITY
[0001] The present application claims priority from Japanese patent
application JP 2011-109207 filed on May 16, 2011, the content of
which is hereby incorporated by reference into this
application.
BACKGROUND OF THE INVENTION
[0002] This invention relates to a transponder that performs
bidirectional conversion between a client-side signal and a
transmission path-side signal, and more particularly, to a
transponder that determines a connection destination of an
interface at which the client-side signal is input/output.
[0003] In a transmission system (optical transmission system) in
which a client device and another client device opposed to the
client device are connected to each other through a transmission
path, it is necessary to notify the client device of the occurrence
of a failure when the failure has occurred in the transmission path
or the like.
[0004] As one known example, the transmission system includes two
terminal equipments connected to two client devices, and the
terminal equipments are connected to each other through a
transmission path. The terminal equipment includes one transponder
that performs bidirectional conversion between a client-side signal
used for communication to the client device and a transmission
path-side signal used for communication to the transmission path.
When a signal is output from the client device, the transponder of
the terminal equipment connected to the client device converts a
client-side signal into a transmission path-side signal and outputs
the converted signal to the transmission path side. On the other
hand, when a signal is input to the client device, the transponder
converts a transmission path-side signal into a client-side signal
and inputs the converted signal to the client device.
[0005] Further, one transmission path has a fixed length, and
hence, the length of the transmission path can be enlarged by
providing at least one repeater between two terminal equipments.
This is because two transmission paths are connected to one
repeater. The repeater includes two transponders. One of the
transponders converts a transmission path-side signal into a
client-side signal, and the other converts a client-side signal
output from one transponder into a transmission path-side
signal.
[0006] The transponder includes a client-side interface connected
to the client device or the other transponder and a transmission
path-side interface connected to the transmission path.
[0007] The client-side interface of the transponder provided in the
terminal equipment is connected to the client device, and the
transmission path-side interface is connected to the transmission
path. The client-side interface provided in the repeater is
connected to the other transponder, and the transmission path-side
interface is connected to the transmission path.
[0008] In the following description, the terminal equipment and the
repeater are sometimes collectively referred to "communication
device".
[0009] As a system of notifying the client device of the occurrence
of a failure in the above-mentioned transmission system, there are
known a system in which failure information indicating the
occurrence of a failure is included in an overhead part of a light
signal and a system in which a frame for transferring the failure
information is generated and the frame is transferred to the client
device.
[0010] For example, in the case of the former system, in a
synchronous digital hierarchy (SDH) system, a signal called an
alarm indication signal (AIS) is included in a frame of a
transmission signal flowing through the transmission path, and
thus, failure information is transferred to the client device.
[0011] Further, in the case of the latter system, in an Ethernet
system of the 10-Gigabit Ethernet, a failure transfer function
called link fault signaling (LFS) is standardized.
[0012] However, in order for a communication device to detect the
failure information, it is necessary to decode a light signal at
high speed to read a warning signal. Therefore, there is a problem
in that the cost for the communication device rises.
[0013] In order to lower the cost for the communication device, the
following method is known. When a failure has occurred, the output
of a light signal is stopped at a client-side interface of a
transponder to notify a client device of the occurrence of the
failure, and a client loss of signal (LOS) signal that notifies the
client device of the occurrence of the failure is output through
use of an Ether-OAM signal at a transmission path-side interface
(for example, see Japanese Patent Application Laid-open No.
2010-81223).
[0014] This method is described with reference to FIGS. 10 to
12.
[0015] FIG. 10 is an explanatory diagram of a failure notification
method in the case where a failure has occurred in a transmission
path in a conventional example.
[0016] A transmission system includes a client device 100, a
terminal equipment 200, a terminal equipment 500, and a client
device 600. The terminal equipments 200 and 500 are connected to
each other through a transmission path 440.
[0017] The terminal equipment 200 includes a transponder 420 and an
optical multiplexer 430. The transponder 420 converts a client-side
signal from the client device 100 into a transmission path-side
signal. The optical multiplexer 430 multiplexes the transmission
path-side signal from the transponder 420 and outputs the resultant
signal to the transmission path 440 side.
[0018] The terminal equipment 500 includes a transponder 460 and an
optical de-multiplexer 450. The optical de-multiplexer 450
de-multiplexes the transmission path-side signal from the
transmission path 440 and outputs the resultant signal to the
transponder 460. The transponder 460 converts the transmission
path-side signal output from the optical de-multiplexer 450 into a
client-side signal and outputs the converted client-side signal to
the client device 600.
[0019] It is assumed that a failure such as the disconnection of an
optical fiber has occurred in the transmission path 440 (51). In
this case, a light signal does not reach a downstream side from a
place where the failure has occurred. Therefore, the transponder
460 provided in the terminal equipment 500 detects an LOS (52) and
stops the output from the client-side interface connected to the
client device 600 (53). The client device 600 detects the LOS (54)
and can detect that some failure has occurred in the transmission
system.
[0020] FIG. 11 is an explanatory diagram of a failure notification
method in the case where a failure has occurred between the client
device 100 and the terminal equipment 200 in the conventional
example.
[0021] The configuration of the transmission system illustrated in
FIG. 11 is the same as that of the transmission system illustrated
in FIG. 10, and hence, the description thereof is omitted.
[0022] When a failure such as the disconnection of an optical fiber
has occurred between the client device 100 and the terminal
equipment 200 (51), a light signal does not reach a downstream side
from a place where the failure has occurred. Therefore, the
transponder 420 provided in the terminal equipment 200 detects an
LOS (52) and outputs a client LOS signal from the transmission
path-side interface to the downstream side (55).
[0023] When the client LOS signal from the transponder 420 is input
to the transponder 460, the transponder 460 stops the output from
the client-side interface connected to the client device 600 (53).
The client device 600 detects the LOS (54) and can detect that some
failure has occurred in the transmission system.
[0024] FIG. 12 is an explanatory diagram of a failure notification
method in a multi-stage transmission system of the conventional
example.
[0025] A transmission system illustrated in FIG. 12 is a
multi-stage transmission system which includes two repeaters 300
and 400 (hereinafter, collectively referred to as "repeater 300")
and in which a transmission path is extended. It should be noted
that the transmission system including at least one repeater 300 is
called a multi-stage transmission system.
[0026] Client devices 100 and 600 illustrated in FIG. 12 are the
same as the client devices 100 and 600 illustrated in FIG. 10, and
terminal equipments 200 and 500 illustrated in FIG. 12 are the same
as the terminal equipments 200 and 500 illustrated in FIG. 10, and
hence, the descriptions thereof are omitted.
[0027] The repeater 300 includes an optical de-multiplexer 640, a
transponder 650, a transponder 660, and an optical multiplexer
670.
[0028] The optical de-multiplexer 640 is the same as the optical
de-multiplexer 450 provided in the terminal equipment 500
illustrated in FIG. 10, and the optical multiplexer 670 is the same
as the optical multiplexer 430 provided in the terminal equipment
200 illustrated in FIG. 10, and hence, the descriptions thereof are
omitted.
[0029] A transmission path-side interface of the transponder 650 is
connected to the optical de-multiplexer 640 and a client-side
interface of the transponder 650 is connected to the transponder
660. The transponder 650 converts a transmission path-side signal
into a client-side signal.
[0030] A transmission path-side interface of the transponder 660 is
connected to the optical de-multiplexer 670 and a client-side
interface of the transponder 660 is connected to the transponder
650. The transponder 660 converts a client-side signal into a
transmission path-side signal.
[0031] The configuration of the repeater 400 is the same as that of
the repeater 300, and hence, the description thereof is
omitted.
[0032] When a failure such as the disconnection of an optical fiber
has occurred between the client device 100 and the terminal
equipment 200 (810), a light signal does not reach a downstream
side from a place where the failure has occurred. Therefore, the
transponder 420 provided in the terminal equipment 200 detects an
LOS (820) and outputs a client LOS signal from the transmission
path-side interface (830).
[0033] When the client LOS signal is input to the transponder 650
provided in the repeater 300, the transponder 650 stops the output
of the client-side interface (840).
[0034] The transponder 660 detects the LOS based on the stop of the
output from the client-side interface by the transponder 650 (850),
and outputs a client LOS signal from the transmission path-side
interface (860).
[0035] When the client LOS signal is input to the transponder 690
provided in the repeater 400, the transponder 690 stops the output
of the client-side interface (870).
[0036] The transponder 700 detects the LOS based on the stop of the
output from the client-side interface by the transponder 690 (880),
and outputs a client LOS signal from the transmission path-side
interface (890).
[0037] When the client LOS signal is input to the transponder 450
provided in the terminal equipment 500, the transponder 450 stops
the output of the client-side interface (900).
[0038] The client device 600 detects the LOS (910) and can detect
that some failure has occurred in the transmission system.
[0039] In the multi-stage transmission system illustrated in FIG.
12, an output to a client device is stopped so as to notify the
client device of the occurrence of a failure from the viewpoint of
using the transponders provided in the terminal equipments 200 and
500 and the transponders provided in the repeaters 300 and 400 in
common. Therefore, in all the transponders, when a client LOS
signal is input to a transmission path-side interface, the output
from the client-side interface is stopped.
[0040] Therefore, all the transponders connected to the
transmission path output client LOS signals in spite of the fact
that a failure has occurred at one place of the client-side
interface, and hence, it is difficult for a manager to check all
the client LOS signals to identify the failure place.
SUMMARY OF THE INVENTION
[0041] It is an object of this invention to provide a transponder
that allows a manager to easily identify a failure place with the
common use of transponders provided in repeaters and terminal
equipments.
[0042] According to an aspect of the present invention, there is
provided a transponder for performing bidirectional conversion
between a client-side signal used for communication to a client
device and a transmission path-side signal used for communication
to a transmission path, the transponder comprising: a client-side
interface for inputting/outputting the client-side signal, which is
coupled to one of another client-side interface and the client
device; a transmission path-side interface for inputting/outputting
the transmission path-side signal; a connection determining unit
for determining which of the another client-side interface and the
client device is coupled to the client-side interface; and a
transmission signal generating unit for outputting, in a case where
a state signal indicating a state on a transmission path side is
input to the transmission path-side interface, a transmission
signal indicating that the state signal has been input, from the
client-side interface, wherein: the connection determining unit has
a recognition signal output unit for outputting, from the
client-side interface, a recognition signal for determining that
the another client-side interface is coupled to the client-side
interface; the connection determining unit determines that the
another client interface is coupled to the client-side interface in
a case where the recognition signal is input to the client-side
interface; and the transmission signal generating unit changes a
form of the transmission signal to be output from the client-side
interface, based on a determination result obtained by the
connection determining unit.
[0043] According to a mode of this invention, it can be provided
that a transponder allows a manager to easily identify a failure
place with the common use of transponders provided in repeaters and
terminal equipments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0044] The present invention can be appreciated by the description
which follows in conjunction with the following figures,
wherein:
[0045] FIG. 1 is a diagram illustrating a configuration of a
transmission system according to an embodiment of this
invention;
[0046] FIG. 2 is a block diagram illustrating a configuration of
terminal equipments according to an embodiment of this
invention;
[0047] FIG. 3 is a block diagram illustrating a configuration of
the repeaters according to an embodiment of this invention;
[0048] FIG. 4 is an explanatory diagram of the conversion of a
signal in a transmission system having no repeaters of an
embodiment of this invention;
[0049] FIG. 5 is an explanatory diagram of a conversion of a signal
in a multi-stage transmission system of an embodiment of this
invention;
[0050] FIG. 6 is a block diagram illustrating a configuration of
the transponder according to an embodiment of this invention;
[0051] FIG. 7 is an explanatory diagram of a failure notification
method in the transmission system according to an embodiment of
this invention;
[0052] FIG. 8 is a sequence diagram illustrating a sequence until
two transponders according to an embodiment of this invention
determine back-to-back connection;
[0053] FIG. 9 is a flowchart of a connection determination process
by a transponder according to the embodiment of this invention;
[0054] FIG. 10 is an explanatory diagram of a failure notification
method in a case where a failure has occurred in a transmission
path in a conventional example;
[0055] FIG. 11 is an explanatory diagram of a failure notification
method in a case where a failure has occurred between a client
device and a terminal equipment in a conventional example; and
[0056] FIG. 12 is an explanatory diagram of a failure notification
method in a multi-stage transmission system of a conventional
example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0057] Hereinafter, an embodiment of this invention is described
with reference to FIGS. 1 to 9.
[0058] FIG. 1 is a diagram illustrating a configuration of a
transmission system according to the embodiment of this
invention.
[0059] The transmission system includes client devices 1 and 6,
terminal equipments 2 and 5, and repeaters 3 and 4, and connects
the client device 1 and the client device 6 which are placed at two
points at a distance.
[0060] A signal from the client device 1 to the client device 6 is
transmitted from the client device 1 to the client device 6 via the
terminal equipment 2, the repeater 3, the repeater 4, and the
terminal equipment 5. A signal from the client device 6 is
transmitted to the client device 1 in the same way.
[0061] Further, the terminal equipments 2 and 5 and the repeaters 3
and 4 (hereinafter, collectively referred to as "communication
device") are connected to a monitoring control device 8 via a
monitoring network 7. The communication device outputs a warning
signal of a client loss-of-signal (LOS) signal to another
communication device and also outputs the warning signal to the
monitoring network 7. Therefore, the monitoring control device 8
can monitor the warning signal output from the communication device
at real time.
[0062] FIG. 2 is a block diagram illustrating a configuration of
the terminal equipments 2 and 5 according to the embodiment of this
invention.
[0063] The terminal equipments 2 and 5 (hereinafter, collectively
referred to as "terminal equipment") includes transponders 11 to 13
(hereinafter, collectively referred to as "transponder"), an
optical multiplexer 14, an optical de-multiplexer 15, and a
monitoring control unit 16.
[0064] The transponder performs bidirectional conversion between a
client-side signal used for communication to the client devices 1
and 6 (hereinafter, collectively referred to as "client device")
and a transmission path-side signal used for communication to a
transmission path.
[0065] Specifically, the transponder converts a client-side signal
from the client device into a transmission path-side signal having
a predetermined wavelength capable of wavelength multiplexing and
outputs the transmission path-side signal to the optical
multiplexer 14. In this case, the transponder may add an
error-correcting code and data for remote control to the
client-side signal before the conversion.
[0066] Further, the transponder converts a transmission path-side
signal output from the optical de-multiplexer 15 into a client-side
signal and outputs the client-side signal to the client device.
[0067] The transponder includes a client-side interface for
input/output of the client-side signal and a transmission path-side
interface for input/output of the transmission path-side
signal.
[0068] The optical multiplexer 14 multiplexes transmission
path-side signals from a plurality of transponders and outputs the
multiplexed signals to a transmission path formed of one optical
fiber.
[0069] The optical de-multiplexer 15 de-multiplexes a signal input
from a transmission path and outputs the de-multiplexed signal to
the transponder.
[0070] The monitoring control unit 16 monitors the optical
input/output level, the operation state, and the like of the
transponders, the optical multiplexer 14, and the optical
de-multiplexer 15 provided in the terminal equipment, and sends an
LOS signal to the monitoring network 7 when detecting a
failure.
[0071] FIG. 3 is a block diagram illustrating a configuration of
the repeaters 3 and 4 according to the embodiment of this
invention.
[0072] Hereinafter, the repeaters 3 and 4 are collectively referred
to as "repeater".
[0073] As to the repeater, the following systems are known: a
system of using an optical amplifier without converting a signal
between a light signal and an electric signal; and a system of
using an optical regenerative repeater unit for converting a light
signal into an electric signal and thereafter converting the
electric signal into a light signal. The repeater of this
embodiment is configured by connecting client-side interfaces of
two transponders. The connection between the client-side interface
of one transponder and the client-side interface of another
transponder is referred to as back-to-back connection.
[0074] The repeater includes optical de-multiplexers 21 and 30,
optical multiplexers 22 and 29, transponders 23 to 28, and a
monitoring control unit 31.
[0075] Each of the optical de-multiplexers 21 and 30 de-multiplexes
a signal input from a transmission path and outputs the
de-multiplexed signal to the transponder. The optical
de-multiplexer 21 de-multiplexes a signal from a first transmission
path, and the optical de-multiplexer 30 de-multiplexes a signal
from a second transmission path.
[0076] Each of the optical multiplexers 22 and 29 multiplexes
signals from a plurality of transponders and outputs the
multiplexed signal to a transmission path. The optical multiplexer
22 multiplexes signals from the transponders 23, 25, and 27 and
outputs the multiplexed signal to the first transmission path. The
optical multiplexer 29 multiplexes signals from the transponders
24, 26, and 28 and outputs the multiplexed signal to the second
transmission path.
[0077] The client-side interface of the transponder 23 is connected
to the client-side interface of the transponder 24.
[0078] For example, when a signal is input from the first
transmission path side, the signal is de-multiplexed by the optical
de-multiplexer 21, and the de-multiplexed signal is input to the
transmission path-side interface of the transponder 23. The
transponder 23 converts the de-multiplexed signal into a
client-side signal and outputs the converted signal from the
client-side interface to the transponder 24.
[0079] The transponder 24 converts the signal, which has been
converted into the client-side signal, into a transmission
path-side signal and outputs the converted signal from the
transmission path-side interface to the optical multiplexer 29. The
optical multiplexer 29 multiplexes the signal from the transponder
24 with the signals from the other transponders 26 and 28 and
outputs the multiplexed signal to the second transmission path.
[0080] Even when a signal is input to the transponder 24 from the
second transmission path, the same signal conversion process is
performed. The same applies to the transponders 25 and 26, and the
transponders 27 and 28.
[0081] The monitoring control unit 31 monitors the optical
input/output level, the operation state, and the like of the
transponders, the optical multiplexers 22 and 29, and the optical
de-multiplexers 21 and 30 provided in the repeater, and sends an
LOS signal to the monitoring network 7 when detecting a
failure.
[0082] Next, the conversion of a signal of this invention is
described with reference to FIGS. 4 and 5.
[0083] FIG. 4 is an explanatory diagram of the conversion of a
signal in a transmission system having no repeaters of the
embodiment of this invention.
[0084] In the transmission system illustrated in FIG. 4, the
terminal equipments 2 and 5 are connected to each other via a
transmission path 44. The client device 1 is connected to the
terminal equipment 2, and the client device 6 is connected to the
terminal equipment 5.
[0085] A signal (client-side signal) from the client device 1 is
input to the client-side interface of a transponder 42. The
transponder 42 converts the client-side signal input to the
client-side interface into a transmission path-side signal and
outputs the transmission path-side signal from the transmission
path-side interface to an optical multiplexer 43. The optical
multiplexer 43 multiplexes the input transmission path-side signal
with a transmission path-side signal having another wavelength and
outputs the multiplexed signal to a transmission path.
[0086] The transmission path-side signal output to the transmission
path is input to the optical de-multiplexer 45 provided in the
terminal equipment 5. The optical de-multiplexer 45 de-multiplexes
the input transmission path-side signal into a predetermined
wavelength and outputs the de-multiplexed signal to the
transmission path-side interface of a transponder 45.
[0087] When the transponder 46 receives the transmission path-side
signal from the transmission path-side interface, the transponder
46 converts the input transmission path-side signal into a
client-side signal and outputs the client-side signal from the
client-side interface to the client device 6.
[0088] FIG. 5 is an explanatory diagram of the conversion of a
signal in a multi-stage transmission system of the embodiment of
this invention.
[0089] In the multi-stage transmission system illustrated in FIG.
5, two transponders are back-to-back connected to each other in the
repeater. When the repeater is configured by back-to-back
connecting two transponders, the transponders can be used in common
with another communication device, and a transmission path
constituting the network that has already been constructed can be
extended, as compared with the repeater using an optical
amplifier.
[0090] In the configuration of the multi-stage transmission system
illustrated in FIG. 5, the same configurations as those of the
transmission system illustrated in FIG. 4 are denoted by the same
reference numerals, and the description thereof is omitted.
[0091] The transmission path-side signal output from the optical
multiplexer 43 of the terminal equipment 2 is input to an optical
de-multiplexer 64 of the repeater 3 via a transmission path.
[0092] The optical de-multiplexer 64 de-multiplexes the input
transmission path-side signal into a predetermined wavelength and
outputs the de-multiplexed signal to the transmission path-side
interface of a transponder 65.
[0093] The transponder 65 converts the transmission path-side
signal input to the transmission path side interface into a
client-side signal and outputs the converted client-side signal
from the client-side interface to a transponder 66.
[0094] The transponder 66 converts the client-side signal input to
the client-side interface into a transmission path-side signal and
outputs the converted transmission path-side signal from the
transmission path-side interface to an optical multiplexer 67.
[0095] The optical multiplexer 67 multiplexes the input
transmission path-side signal with a transmission path-side signal
having another wavelength and outputs the multiplexed signal to a
transmission path.
[0096] The conversion of a signal in the repeater 4 is the same as
that in the repeater 3, and hence, the description thereof is
omitted.
[0097] FIG. 6 is a block diagram illustrating the configuration of
the transponder according to the embodiment of this invention.
[0098] The transponder includes optical modules 91 and 93, a
forward error correction (FEC) circuit 92, a recognition signal
insertion circuit 94, a recognition signal detection circuit 95, a
control circuit 96, and a failure transmission signal insertion
circuit 97.
[0099] The optical module 91 is connected to the FEC circuit 92,
and the FEC circuit 92 is connected to the optical module 93. The
recognition signal insertion circuit 94 and the failure
transmission signal insertion circuit (transmission signal
generating unit) 97 are connected to one of connection lines
connecting the FEC circuit 92 to the optical module 93, that is, a
connection line for outputting a signal to the optical module 93.
Further, the recognition signal detection circuit 95 is connected
to another of the connection lines connecting the FEC circuit 92 to
the optical module 93, that is, a connection line for outputting a
signal to the FEC circuit 92.
[0100] The optical module 91 functions as a transmission path-side
interface that inputs/outputs a transmission path-side signal, and
converts the transmission path-side signal that is a light signal
into an electric signal.
[0101] The optical module 93 functions as a client-side interface
that inputs/outputs a client-side signal, and converts the
client-side signal that is a light signal into an electric
signal.
[0102] The FEC circuit 92 encodes and decodes an error-correcting
code (FEC) contained in the transmission path-side signal.
[0103] The recognition signal insertion circuit 94 inserts, into a
signal, a recognition signal output from the client-side
interface.
[0104] The recognition signal detection circuit 95 detects the
recognition signal from the signal input to the client-side
interface. When the recognition signal detection circuit 95 detects
the recognition signal from the signal input to the client-side
interface, the recognition signal detection circuit 95 notifies the
control circuit 96 of the detection of the recognition signal.
[0105] Further, the recognition signal detection circuit 95 detects
a failure transmission signal from the signal input to the
client-side interface. When the recognition signal detection
circuit 95 detects the failure transmission signal from the signal
input to the client-side interface, the recognition signal
detection circuit 95 notifies the control circuit 96 of the
detection of the failure transmission signal.
[0106] The control circuit 96 controls various circuits. When the
control circuit 96 is notified of the detection of the recognition
signal from the recognition signal detection circuit 95, the
control circuit 96 determines that one client-side interface is
connected to another client-side interface (back-to-back
connection), and outputs an acknowledge (ACK) signal from the
client-side interface.
[0107] Further, when the control circuit 96 is notified of the
detection of the failure transmission signal from the recognition
signal detection circuit 95, the control circuit 96 outputs, from
the transmission path-side interface, a client LOS transmission
signal indicating that a failure has occurred on an upstream
side.
[0108] Thus, the recognition signal insertion circuit 94, the
recognition signal detection circuit 95, the control circuit 96,
and the failure transmission signal insertion circuit 97 function
as a connection determining unit for determining whether or not one
client-side interface is connected to another client-side
interface.
[0109] Further, the recognition signal detection circuit 95 and the
control circuit 96 in the connection determining unit function as a
response signal generating unit for outputting an ACK signal, which
is a response signal with respect to the recognition signal, from
the client-side interface.
[0110] In the case where the connection is determined as
back-to-back connection, when the failure transmission signal
insertion circuit 97 detects a client LOS signal or a client LOS
transmission signal from the transmission path-side interface, the
failure transmission signal insertion circuit 97 outputs a failure
transmission signal from the client-side interface. On the other
hand, in the case where the connection is not determined as
back-to-back connection, when the failure transmission signal
insertion circuit 97 detects a client LOS signal or a client LOS
transmission signal at the transmission path-side interface, the
failure transmission signal insertion circuit 97 stops the output
of the client-side interface to output the failure transmission
signal. The client LOS signal is a signal to be output from the
transmission path-side interface when an LOS is detected at the
client-side interface.
[0111] Thus, a back-to-back connected transponder transmits a
transmission signal without stopping the output of the client-side
interface even when a failure occurs on an upstream side of the
transmission path-side interface of the transponder, and hence, the
output of an unnecessary client LOS signal can be prevented.
[0112] As described above, when the failure transmission signal
insertion circuit 97 detects a client LOS signal or a client LOS
transmission signal at the transmission path-side interface, the
failure transmission signal insertion circuit 97 can change the
form of a failure transmission signal to be output from the
client-side interface based on the determination result of the
connection determining unit.
[0113] FIG. 7 is an explanatory diagram of a failure notification
method in the transmission system of the embodiment of this
invention.
[0114] The configuration of the transmission system illustrated in
FIG. 7 is the same as that of the transmission system illustrated
in FIG. 5, and hence, the description thereof is omitted.
[0115] When a failure such as the disconnection of an optical fiber
occurs between the client device 1 and the terminal equipment 2
(81), the transponder 42 provided in the terminal equipment 2
detects an LOS (82) and outputs a client LOS signal from the
transmission path-side interface (83). The client LOS signal is
also output to the monitoring network 7 as a warning signal.
[0116] Next, when the client LOS signal is input to the
transmission path-side interface of the transponder 65 provided in
the repeater 3, the transponder 65 outputs a transmission signal
from the client-side interface because the transponder 65 is
back-to-back connected to the transponder 66 (84).
[0117] When the transmission signal is input to the client-side
interface of the transponder 66 provided in the repeater 3, the
transponder 66 outputs a client LOS transmission signal for
notifying the downstream side of the occurrence of the failure from
the transmission path-side interface to a transmission path (85).
The client LOS transmission signal is not output to the monitoring
network 7 as a warning signal.
[0118] Next, when the client LOS transmission signal is input to
the transmission path-side interface of a transponder 69 provided
in the repeater 4, the transponder 69 outputs a transmission signal
from the client-side interface because the transponder 69 is
back-to-back connected to a transponder 70 (86A).
[0119] When the transmission signal is input to the client-side
interface of the transponder 70 provided in the repeater 4, the
transponder 70 outputs a client LOS transmission signal from the
transmission path-side interface to a transmission path (86B).
[0120] Next, when the client LOS transmission signal is input to
the transmission path-side interface of the transponder 46 provided
in the terminal equipment 5, the transponder 46 stops the output of
the client-side interface because the transponder 46 is not
back-to-back connected (87).
[0121] Then, the client device 6 detects an LOS (88) and can detect
that some failure has occurred in the transmission system.
[0122] Thus, in this embodiment, when a signal (client LOS signal
or client LOS transmission signal) indicating the occurrence of a
failure is input to the transmission path-side interface of the
transponder, the transponder outputs a transmission signal from the
client-side interface if the transponder is back-to-back connected.
Further, if the transponder is not back-to-back connected, in other
words, if the client device is connected to the client-side
interface, the transponder stops the output. Therefore, another
transponder that is back-to-back connected to the transponder
detects an LOS at the client-side interface and can prevent the
client LOS signal from being output from the transmission path-side
interface.
[0123] Accordingly, the manager of the monitoring control device 8
can easily determine that a failure has occurred on the upstream
side of a device that has output a client LOS signal.
[0124] FIG. 7 illustrates that a failure occurs between the client
device 1 and the terminal equipment 2. Next, the case where a
failure occurs in a transmission path between the terminal
equipment 2 and the repeater 4 is described with reference to FIG.
7.
[0125] No signal is input to the transmission path-side interface
of the transponder 65 of the repeater 3, and hence, the transponder
65 detects an LOS at the transmission path-side interface. In this
case, the transponder 65 stops the output of the client-side
interface.
[0126] Specifically, the transponder of this embodiment is set so
as to stop the output of the client-side interface when detecting
an LOS at the transmission path-side interface and so as to output
a client LOS signal from the transmission path-side interface when
detecting an LOS at the client-side interface.
[0127] The output of the client-side interface of the transponder
65 is stopped, and hence, when the transponder 66 detects an LOS at
the client-side interface, the transponder 66 outputs a client LOS
signal from the transmission path-side interface.
[0128] The subsequent processes are the same as those in the case
where a failure occurs between the client device 1 and the terminal
equipment 2, and hence, the descriptions thereof are omitted.
[0129] As described above, even when an LOS is detected at the
transmission path-side interface of a transponder, the output of
the client-side interface of the transponder is stopped. Therefore,
a client LOS signal is output from the transmission path-side
interface of another transponder that is back-to-back connected to
the transponder. Then, a transponder placed on a downstream side of
the transponder that has output the client LOS signal does not
output a client LOS signal, and hence, the manager can easily
identify a failure point.
[0130] FIG. 8 is a sequence diagram illustrating a sequence until
two transponders 65 and 66 of the embodiment of this invention
determine back-to-back connection.
[0131] Each transponder illustrated in FIG. 8 corresponds to each
transponder illustrated in FIG. 7. In FIG. 8, the repeater 4 is
omitted, and hence, it is assumed that the transponder 46 of the
terminal equipment 5 is connected to the transponder 66 provided in
the repeater 3.
[0132] First, the transponder 65 is powered on (100). In the case
where the transmission path-side interface of the transponder 65 is
not connected to the transponder 42, nothing is input to the
transmission path-side interface of the transponder 65 (102), and
hence, the transponder 65 stops the output of the client-side
interface (101).
[0133] Examples of the case where the transmission path-side
interface of the transponder 65 is not connected to the transponder
42 include a case where an optical fiber for connecting the
transmission-side interface of the transponder 65 to the
transmission path-side interface of the transponder 42 is not
connected and a case where the transponder 42 is not powered
on.
[0134] Next, when the transmission path-side interface of the
transponder 42 is connected to the transmission path-side interface
of the transponder 65, the transponder 42 outputs a signal from the
transmission path-side interface, and when the transponder 65
detects that the signal has been input to the transmission
path-side interface, the transponder 65 determines that the
transmission path-side interface has been connected to the
transponder 42 (103). Then, the transponder 65 outputs a normal
signal from the client-side interface (104). Unlike a recognition
signal, the normal signal is a signal capable of being detected by
the transponder regardless of whether the signal is input to the
client-side interface or the transmission path-side interface of
the transponder.
[0135] In the same way as in the connection between the
transponders 42 and 65, when the transponders 46 and 66 are not
connected, nothing is input to the transmission path-side interface
of the transponder 66 (105), and when a signal is input to the
transmission path-side interface of the transponder 66, it is
determined that the transponders 46 and 66 have been connected to
each other (106). Then, the transponder 66 outputs a normal signal
from the client-side interface (107).
[0136] The transponders 65 and 66 confirm that a link is
established between the client-side interfaces based on the input
of the output signal.
[0137] Then, one of the transponders outputs a recognition signal
from the client-side interface when a normal signal is input from
the other transponder to the client-side interface (108). In FIG.
8, the normal signal is input to the transponder 66 prior to the
transponder 65, and hence, the transponder 66 outputs a recognition
signal first.
[0138] When the transponder receives the recognition signal at the
client-side interface, the transponder determines that the
connection is back-to-back connection, and outputs an ACK signal
from the client-side interface (109).
[0139] Even when the recognition signal is input to the
transmission path-side interface, the recognition signal detection
circuit 95 illustrated in FIG. 6 does not detect the recognition
signal, and hence, the transponder does not output an ACK signal.
This is because the recognition signal is constituted by a special
pattern not used for an ordinary signal.
[0140] Thus, when the transponders 65 and 66 determine that the
connection is back-to-back connection, the transponders 65 and 66
start an operation in a back-to-back mode (110, 111).
[0141] On this occasion, when a failure has occurred between the
client device 1 and the terminal equipment 2 in the same way as in
FIG. 7, the transponder 42 detects that there is no input to the
client-side interface, and outputs a client LOS signal from the
transmission path-side interface (83).
[0142] When the transponder 65 receives the client LOS signal at
the transmission path-side interface, the transponder 65 outputs a
transmission signal from the client-side interface because the
transponders 65 and 66 are back-to-back connected (84).
[0143] When the transponder 66 receives the transmission signal at
the client-side interface, the transponder 66 outputs a client LOS
transmission signal from the transmission path-side interface
(85).
[0144] When the transponder 46 receives the client LOS signal at
the transmission path-side interface, the transponder 46 stops the
output of the client-side interface because the transponder 46 is
not back-to-back connected (87).
[0145] FIG. 9 is a flowchart of a connection determination process
by the transponder of the embodiment of this invention.
[0146] The connection determination process is performed at a
predetermined timing for a predetermined period of time after
power-on by the control circuit 96 provided in the transponder.
[0147] First, the control circuit 96 determines whether or not some
signal has been input to the transmission path-side interface
(901).
[0148] When it is determined in the process of Step 901 that no
signal has been input to the transmission path-side interface, the
connection determination process is ended because no connection is
established on the transmission path side.
[0149] On the other hand, when it is determined in the process of
Step 901 that some signal has been input to the transmission
path-side interface, the control circuit 96 outputs a normal signal
from the client-side interface (902).
[0150] Next, the control circuit 96 determines whether or not the
normal signal has been input to the client-side interface
(903).
[0151] When it is determined in the process of Step 903 that the
normal signal has not been input to the client-side interface, the
connection determination process is ended because no connection is
established on the client side.
[0152] On the other hand, when it is determined in the process of
Step 903 that the normal signal has been input to the client-side
interface, the control circuit 96 outputs a recognition signal from
the client-side interface (904).
[0153] Next, the control circuit 96 determines whether or not a
response signal with respect to the recognition signal output in
the process of Step 904 has been input to the client-side interface
(905).
[0154] When it is determined in the process of Step 905 that the
recognition signal has been input to the client-side interface, it
is determined that the connection is back-to-back connection (906)
and the connection determination process is ended.
[0155] On the other hand, when it is determined in the process of
Step 905 that the recognition signal has not been input to the
client-side interface, it is determined that the connection is not
back-to-back connection (907) and the connection determination
process is ended.
[0156] It should be noted that, when the determination as to
whether or not the connection is back-to-back connection has been
made in the process of Step 906 or 907, the connection
determination process is not repeated.
[0157] Further, in FIG. 9, whether or not the connection is
back-to-back connection is determined based on whether or not the
recognition signal has been input to the client-side interface.
However, the control circuit 96 may determine that the connection
is back-to-back connection when an ACK signal with respect to the
recognition signal output in the process of Step 904 has been
input, and may determine that the connection is not back-to-back
connection when the ACK signal has not been input.
[0158] Although the notification of a failure occurring on the
upstream side of the transponder has been described in this
embodiment, a state (including a failure) as well as a failure on
the upstream side of the transponder may be notified. In this case,
the client LOS signal and the client LOS transmission signal
illustrated in FIG. 7 become state signals.
[0159] As described above, in this embodiment, the transponder
outputs a recognition signal from the client-side interface and
determines whether or not connection is back-to-back connection
based on the recognition signal. Then, if the connection is
back-to-back connection, when a state signal is input from the
transmission path-side interface, a transmission signal is output
from the client-side interface, and the output of the client-side
interface is stopped if the connection is not back-to-back
connection.
[0160] Thus, the transponders in the repeater and the terminal
equipment can be used in common, and the output of an unnecessary
client LOS signal can be prevented, which facilitates the
identification of a failure point.
[0161] While the present invention has been described in detail and
pictorially in the accompanying drawings, the present invention is
not limited to such detail but covers various obvious modifications
and equivalent arrangements, which fall within the purview of the
appended claims.
* * * * *